Safety device for high potential electrical circuits



Feb. 2, 1937. R C, HYDE 2,069,250

SAFETY DEVICE FOR HIGH POTENTIAL ELECTRICAL CIRCUITS Filed DeG. 5, 1935 3 Sheets-Sheet 1 R. C. HYDE Feb. 2, 1937.

SAFETY DEVICE FOR HIGH POTENTIAL ELECTRICAL CIRCUITS Filed Dec. 5, 1935 3 Sheets-Sheet 2 flltarney;

Patented Feb. 2, 1937 UNITED STATES PATENT OFFICE SAFETY DEVICE FOR HIGH POTENTIAL ELECTRICAL CIRCUITS ware I Application December 5, 1933, Serial No. 700,979

1 Claim.

My invention relates to electrical apparatus employing high potential electrical current, and has particular reference to a safety device which may be employed to limit the length of the arc which may be drawn in such circuits.

In certain types of high potential electrical apparatus, such as electrotherapeutic lamps, it is common practice to employ high potential current to the electrical apparatus through flexible conductors, and to use plug type connectors for the purpose of connecting the electrical apparatus with a suitable source of high potential electrical supply. This is particularly true in apparatus such as is commonly employed for the production of ultraviolet ray emanations for the purpose of treating the human body, such apparatus usually incorporating a transformer, the primary `winding of which is connected to a suitable source of low voltage supply, while the secondary winding of which is arranged to be connected to suitable receptacles into which may be plugged flexible conductors leading high potential current to the lamps or other devices which are employed for producing the ultraviolet ray emanatio'ns.v When any of such plug connections are used there is'danger that some person handling the machine will inadvertently remove the plug from the receptacle without first disconnecting the low voltage from the transformer, or without first opening the primary winding circuit for the transformer and in such instance the high potential current will tend to arc between the terminals in the receptacles and the terminals upon the plug, thereby exposing the person handling the machine to severe shocks and burns from such arcs.

It is, therefore, an object of my invention to provide a safety device which may be readily incorporated in the circuit connections of the transformer and electrical apparatus which will insure that in disconnecting the lamp or other electrical apparatus on the high potential side of the transformer it will automatically result in a definite and positive limitation of the length of arcwhich may be drawn and that such arc will be limited to such short distance as to prevent any injury to the person handling the machine. l

Another object of the invention is to provide a device for automatically limiting the arc which can be drawn on the high potential side of the transformer.

Another object of the invention is to `provide a device for automatically limiting the length of the arc which may be drawn on the high poten- (Cl. 20o- 118) tial side of. the transformer and which will automatically short-circuit the high potential winding of the transformer as soon as any arcing condition arises. l

Another object of my invention is to provide a device as set forth in the preceding paragraph in which such device will automatically maintainthe high potential side of the transformer short-circuited duringlthe entire time that conditions exist which might result in arcing.

Other objects and advantages will be apparent from a study of the following specifications, read in connection with the accompanying drawings,

wherein Figure l is an elevational view of an electrotherapeutic lamp wihch may be employed in the practice of my invention;

Fig. 2 is an exploded sectional view of a plug and receptacle connection which may be employed in the practice of my invention;

Fig. 3 is a detailed view of a switch operating element which may be employed in the practice of uw invention;

Fig. 4 is a detail sectional view of a spark gap which may be employed with my invention;

Fig. 5 is a plan view of a receptacle which may be employed for connecting and disconnecting electrical apparatus in accordance with my invention;

Fig. 6 is a plan view of the rear plate of the receptacle shown in Fig. 5;

Fig. 7 is a diagrammatic view illustrating a wiring'system which may be employed with my invention; and

Fig. 8 is a diagrammatic view illustrating the modified form of my invention.

Referring to the drawings, I have illustrated one form of electrical apparatus which employs a high potential electric current for its operation, such apparatus being shown herein as in the form of an electrotherapeutic lamp commonly employed by physicians and in hospitals for the purpose of irradiating portions of the human body with ultraviolet rays. Such apparatus is illustrated as including a suitable stand or base I upon the upper end of which is mounted a box-like housing 2 containing a transformer 3, the primary winding 4 of which may be connected through a suitable switch 5 and a flexible cable 6 to a suitable source of low voltage electric current such as the usual -v. supply lines commonly employed for the distribution of electric current.

The secondary winding 1 of the transformer is illustrated as being connected to a pair of electrical receptacles 8 and 9 which will permit the connection therewith of various types of ultraviolet ray generators which willemploy the high potential electricv current for their operation.

I have illustrated one form of such ultraviolet ray generator including what is known as a body burner I9 which may be of any wellknown construction, usually surrounded by and supported by a hood or reflector I I rigidly mounted upon one end I2 of a tubular bracket I3 which in turn is slidably mounted in a tubular support I4 secured upon brackets I4 mounted upon the upper side of the transformer housing 2. Such mounting permits the sliding of the burner I0 longitudinally relative to the transformer housing 2, and also permits the same to be rotated along the axis parallel to the major axis of the transformer housing 2 to adjust the body burner to any desired position to direct .the ultraviolet rays produced thereby to any desired portion of the human body to be treated.

In view of the fact that it is necessary to adjust the position of the burner I0, it is desirable that the high potential electric current for the burner be supplied through a suitable flexible cable or conductor I5 and that such cable be connected to the burner by a detachable connector or plug connection I6 which may be received in a suitable receptacle I1 mounted upon the end of the tubular bracket I3, while the opposite end of the cable I5 is provided with a suitable plug I8 receivable in either the receptacle 8 or the receptacle 9 mounted upon the transformer housing 2.

I have also illustrated a second type of burner which may be employed for the treatment of certain portions of the body, this apparatus being illustrated as an orificial burner I9, the lamp of which constitutes an elongated narrow tube for producing the ultraviolet rays which isV mounted in a suitable handle 20, one end of which is provided with a plug connection 2I receivable in a suitable receptacle 22, to which is secured a flexible cable 23 the opposite end of which is provided with a plug connection 24 insertable in and connectible with the receptacle 8 or 9 on the transformer housing 2.

The particular form of plug and receptacle connector which can be employed for connecting the high potential side of the transformer with the Various burners, may be of any suitable type, though I prefer the type of burner which, is illustrated and described in the kcopending application of Earl H. Howard, Serial No. 613,014, filed May23, 1932, for Handle for electrical devices, in which is described a plug and receptacle connector the major portions of which are incorporated in Fig. 2 herein. The plug section 25, comprises a suitable plate 26 upon which is mounted a pair of extending electrical terminals 21 and 28 in the form of cylindrical prongs attached to the plate 26 each of which has an enlargement 29 thereon for the purpose of engaging' beneath the top plate 30 of the receptacle section 3l to lock the same in engagement with the receptacle when the terminals are inserted through suitable keyhole shaped openings 32 in the plate 30, and partially rotated relative to the plate 30.

The receptacle section v3l is provided with a pair of metallic terminals 33 and 34 mounted upon the rear plate 35 of the receptacle section, the location of such terminals 33 and 34 being somewhat offset from direct alignment with the enlarged portion 38 of the opening 32 so that in order to make electrical connection between the terminal 33 and the plug terminal 21. it is necessary to insert the terminal 21 and then partially rotate the same relative to the receptacle. The plug section l,25 is illustrated as having a suitable guide stem 31 extending from the center thereof to enter an opening 38 in the top plate 30 of the receptacle and to extend through a corresponding opening 39 in the rear plate 35 of the receptacle so as to center and guide the terminals 21 and 28 into the receptacle and also to constitute ay pivot bearing for determining the axis of rotation of the plug section 25 as the same is partially rotated to engage the receptacle terminals 33 and 34.

As is described in the copending application of Ralph Hyde and Ellis O. Erickson, Serial No. 700,978, filed December 5, 1933 and issued as United States Letters Patent No. 2,002,776 on May 28, 1935, for Safety system for therapeutic lamps, the stern 31 may be provided with a reduced end 40 having one side thereof flattened as indicated at 4I to pass behind a movable contact 42 mounted upon the rear of the plate 35 so that when the plug section 25 is rotated relative to the receptacle, the end 40 will engage and move the movablecontact 42 into engagement with a stationary contact 43 comprising a switch connected in series relation with the primary winding of the transformer 3. Such arrangement insures that the plug must first be inserted and then rotated in order to make an electrical contact between the receptacle terminals 33 and 34 and the plug terminals 21 and 28 and also by such partial rotation the enlargement 29 on the plug terminals 21 and 28 will engage the rear surface of the receptacle plate 30 to lock the same against inadvertent withdrawal therefrom. At the same *time the insertion and rotation of the plug terminals 21 and 28 will close the switch 42-43 to close the circuit to the primary winding to the transformer or to prepare the same to be closed by the manual switch 5. Alsok such arrangement will insure that in order to remove the plug section 25 from the receptacle, or' in order to disconnect the terminals 21-33, 28-34, a partial rotation of the plugin the reverse direction must be made which will first open the switch 42-43 to disconnect the primary winding of the transformer before the terminals 21-33, 28--34 will be disconnected.

With an arrangement such as that described in the Hyde and Erickson application referred to above, the transformer is automatically disconnected before any arcing condition could arise. However, when the receptacle section 3l is to be applied to the burners I0 or I9, it is difficult, if not impossible, to conduct the primary circuit of the transformer to the remote locations of these receptacles and in such instances it is the common practice to dispose with the switch 42 and 43 at these points. Also it may be undesirable to employ the switch 42-43 even upon the receptacles 8 or 9, and such receptacles may be adequately protected against arcing of the high potential current flowing through the terminals of the receptacle and plug connectors by providing a spark gap in each of the receptacles. Such spark gap may be constructed in a very simple manner, as illustrated herein, by providing a pair of strips of` metal 44 and 45, one of which is connected to the receptacle terminal 33 while the other of which is connected to the receptacle terminal 34. The outerA ends of the two metallic 75 strips 44 and 46 are mounted in close relation to each other and preferably have a portion thereof bent outwardly relative to the body'of the strip as indicated at 46 Vand 41. f

By locating the ends 46 and 41 close to each other, for example about Vath inch apart, any disconnection of the plug terminals 21 and 29 from the receptacle terminals 33 and 34 ould cause an arc to be drawn in excess of Vath ch, and such high potential current will find a path of lesser distance and lesser resistance between the ends 46 and 41 of the metal strips 44 and 46. Hence instead of the arc passing between the receptacle terminals and the plug terminals the arc will be confined across the ends 46 and 41 of the metal strips, thus eectively peventing the arc from extending out of the receptacle to a position endangering the person handling the machine.

As is illustrated particularly in Fig. 4, the metal strips 44 and 46 may be formed of bimetallic material so that as soon as an arc is drawn between the ends 46 and 41 the heat generated by such arc will cause the bimetallic strips to expand and approach each other, as indicated in dotted lines in Fig. 4, until the ends 46 and 41 are accurately in metallic engagement with each other so that no further arcing is permitted. Any cooling of the strips which would tend to reform the arc will instantly cause sufcient heat to close the contact between the ends 46 and 41 and thus effectively prevent such arc from attaining any considerable proportions.

It will be understood by those skilled in the art that the type of transformer which is employed in connection with electrotherapeutic apparatus, has its windings so arranged that such transformer may stand indefinitely with its secondary winding short-circuited without causing any injury to the transformer so that the actual Short-circuiting of the secondary winding of the transformer by the contacts 46 and 41 will not result in any damage, but will insure safety of operation for the persons handling the machine.

By employing the spark gap construction illustrated herein in each of the receptacle connections employed with high potential apparatus, any inadvertent disconnection of the connectors will be rendered harmless. Also the spark gap arranged in accordance with my invention will constitute a safety system for the protection of persons handling the machine and persons treated by the machine in the event of breakage of the burners or in the event of breakage of the conductors employed for conducting the high potential current, since as soon as any condition arises which would permit a high potential discharge at any point other than through the lamp of the burner, the arc will pass between the metallic strips 44 and 46 instead of through a path of higher resistance which latterv path might endanger persons working with the machine. Ihe employment of my safety vdevice is, therefore, adaptable to such types of plugs and receptacles as shown in the copending application of Hyde and Erickson, hereinbefore referred to, as a safety measure in addition to the employment of the switch 42 and 43 in the circuit of the primary winding of the transformer.

In Fig. 7 I have illustrated a wiring diagram which may be employed in connection with my invention, such diagram illustrating the connections for the transformer 3 and the connections of the metallic strips 44 and 46 for each of the receptacles. The primary winding 4 of the transformer is illustrated as being connected to a suitable source of electric supply, indicated by the legend 11o-v.. by connecting one terminal 66 of the winding 4 to the source of supply through conductor 6I. The opposite end of the primary winding 4 is illustrated as being provided with a plurality v.of taps each of which is connected by way of conductors 62, 63 and 64 to suitable terminals 66, 66 and 61, respectively. The terminals 66, 66 and 61 may be engaged by a movable contact 66 of the switch 6 to connect any one of these' terminals to a conductor 69 which extends to the movable contacts 42 of the switches 42-43, each of the receptacles 6 and 9. The stationary contacts 43 of these switches may be connected to a conductor 66 which extends to the opposite side of the low voltage supply.

The secondary or high potential winding .1 of the transformer is illustrated as having its opposite ends connected to the receptacle terminals 33 for each of the receptacles, while the terminals 34 of each of these receptacles may be connected through a suitable conductor 6I to the midpoint 62 of the secondary winding 1 and are also preferably grounded upon metallic parts of the machine, as indicated at 63.

The metallic contacts 44 and 46 may therefore be respectively connected in parallel relation with their respective receptacle terminals 33 and 34.

My spark gap may also be employed in connection with signs or other illuminating apparatus employing tubular lamps of the neon type by interposing such spark gap in shunt relation to selected sections of such lamps. For example, in Fig. 8 I have illustrated diagrammatically-a form of wiring connection which can be employed for supplying current from a single transformer 16 to a plurality of tubes 1| 12, 13 and 14, making up a sign display. Each of the tubes 1l, 12, 13 and 14 is respectively connected across a section 16, 16, 11 and 16 of the secondary winding* 19 of the transformer 16. By interposing a spark gap 96 in shunt relation to each of the tubes 1|, 12, 13 and 14, breakage of one of these tubes or disturbance of the circuit from one of these tubes will automatically result in cutting out that part of the circuit which supplies current to that tube, but will permit the continued operation of the remainder of the tubes.

While I have shown and described the preferred embodiment of my invention, I do not wish to be limited to any of the details of construction described herein, except as defined in the appended claim.4

I claim:

In a safety device for electrical apparatus employing high potential electric current derived from a transformer having a high potential winding, a plug and receptacle connections for connecting said electrical apparatus with said highl potential winding, said receptacle having a pair of terminals for the passage of high potential current therethrough, a spark gap comprising a pair of spaced bimetallic members, one connected to each of said terminals to limit an arc which may be drawn between said plug and receptacle connections for the distance defined by said spark gap whereby the heat of an arc drawn between said bimetallic members will reduce the distance therebetween.

RALPHC. HYDE. 

